1. Field of the Invention
The present invention relates to an apparatus for the treatment of blood by extracorporeal circulation and to a process of manufacture of this apparatus.
2. Description of the Related Art
Apparatuses for the treatment of blood by extracorporeal circulation are employed in various medical or paramedical applications such as: treatment of renal insufficiency by dialysis or haemofiltration, plasmapheresis and aphaeresis with therapeutic and nontherapeutic aim, blood oxygenation, immunopurification, and the like.
A common feature of all these apparatuses is that they comprise a blood compartment provided with two accesses, in which, during the treatment in question the patient's blood is circulated. To do this, a blood withdrawal line is connected between a blood vessel of the patient and an access, employed as entry, of the blood compartment; a blood return line is connected between the other access of the blood compartment, employed as exit, and a blood vessel of the patient; and the patient's blood is circulated in this extracorporeal circuit looped onto the patient, by means of a pump, usually placed in the withdrawal line.
The blood compartment of these apparatuses is generally bounded by a portion of the walls of a casing of the apparatus and by a wall of an active member of the apparatus, by means of which the treatment of blood is performed. By way of example, in a dialyser containing hollow fibres, the blood compartment is bounded by the interior of the fibres of a bundle of hollow fibres, constituting a semipermeable membrane, by the external surface of the discs of adhesive employed for attaching the bundle of fibres to the two ends of a tubular casing of the apparatus, and by two end fittings secured to each end of the casing.
All the materials employed in the manufacture of these apparatuses are chosen to be as biocompatible as possible, so that the reactions (coagulation in particular) which take place when the blood comes into contact with a foreign material do not take place or take place at relatively benign levels.
It is known to treat, in bulk or at the surface, the materials intended to be in contact with blood in order to improve their biocompatibility. The known treatments take place either during the manufacture of some part or other of an apparatus (bulk treatment), or after the various parts of the apparatus have been assembled and before sterilization of the apparatus, or, extemporaneously, just before the apparatus is employed.
A problem which is particularly tough to solve arises when attempts are made to improve the biocompatibility of the active member of an apparatus (for example a dialysis membrane) while conforming to the following conditions:
1) the choice of the substance employed for the treatment and the treatment methods must result in the modification of a known active member, this modification having the effect of improving the biocompatibility of the active member while preserving all the known qualities (for example, in the case of a dialysis/haemofiltration membrane: diffusive and convective transfer performance, adsorption capacity for undesirable substances, and the like); PA1 2) sterilization of the apparatus must not affect the treatment; PA1 3) the treatment must not require any special handling by the user.